Reduction of resting spore density of Plasmodiophora brassicae and clubroot disease severity by liming

Abstract

Relationships between the disease severity of clubroot caused by Plasmodiophora brassicae, the soil pH value and the concentration of exchangeable calcium associated with liming were investigated under controlled density of resting spores. Disease indices were lower in the plots treated with lime than in the control plots without lime application. The disease index was significantly lower when lime materials were mixed two weeks before sowing compared with four weeks before sowing. The reduction rate of the disease index was larger for a concentration of 2.0 g kg^?1 than 1.0 g kg^?1 of lime in soil. The density of the resting spores in soil at the time of sowing was significantly reduced by liming. The reduction rate was 17–31 % for calcium cyanamide, 12–29% for dolomite, and 20–39% for calcium carbonate compared with the control plot. It was suggested that the disease severity was influenced by both the soil pH and the content of exchangeable calcium in soil based on the analysis of covariance.     

High sodium/calcium ratios in alkaline Wimmera soils: The role of magnesium and a hypothesis for their development

Sodium calcium ratios are often sufficiently high to limit root growth and result from lower calcium rather than high sodium, and was the focus of this study. A simple model of complex ion formation by magnesium and carbonate was derived, which adequately explained the relationship between pH, calcium, and magnesium, particularly the typical supersaturation of calcium with respect to calcium carbonate. Concentrations of magnesium and calcium declined when excess bicarbonate was applied, and the frequency of adverse sodium/calcium ratios increased. Calcium and magnesium declined proportionately until low concentrations when the proportion of calcium increased. Increased carbonate concentrations could depress calcium and magnesium concentrations to low levels with magnesium being buried in calcium carbonate and unable to redissolve once carbonate levels return to normal. Magnesium soil amendment may be the key to addressing adverse sodium calcium ratios. Plant selection for tolerance to adverse sodium calcium ratios is warranted.     

菱镁矿区土壤质量退化研究

Fourteen soil properties in 17 sampling sites were analyzed to study the soil degradation in a magnesite mining area in Haicheng City,Northeast China.Such areas have hitherto received little attention.The current practices of magnesite mining in this area resulted in degradation of soil quality and specifically led to an increase in soil pH,the ratio of magnesium to calcium,bulk density,clay dispersibility,total magnesium and equivalent calcium carbonate and a decrease in surface soil porosity and available phosphorous.The soil quality in the areas affected by intensive mining activity was obviously worse than that of areas far away from the mine.Four factors were identified and "magnesium factor","pH factor" and "fertility factor",involving 13 soil properties,explained 82% of the total variance in the entire data set.Discriminant analysis showed that the total magnesium,water-soluble calcium and available phosphorous were the most sensitive indicators for soil quality.     

Alleviation of soil acidity improves the performance of oil palm progenies planted on an acid Ultisol

Abstract

Soil acidity is one of the main factors that limit profitable and sustained agricultural production. Oil palm (Elaeis guineensis Jacq.) is mainly planted in acidic soils. In the last years, there has been a stagnated yield and increases in disease incidence and severity worldwide that could be attributed in some extent to soil acidity. This study was conducted to determine the effects of soil acidity alleviation on oil palm seedlings. The effects of ground magnesium limestone or dolomite and magnesium carbonate (0, 1.1, 2.2, 3.3 and 4.4 t ha^?1) applied to an Ultisol dominated by kaolinite (pH in water 4.4) were evaluated on selected morphological, physiological and nutritional characteristics of hybrid (Deli dura × AVROS pisifera) and clonal (clone 366) oil palm progenies under nursery conditions for 8 months. Increasing rates of ground magnesium limestone and magnesium carbonate showed a significant effect on improving soil pH and lowering exchangeable aluminium. The hybrid oil palm showed significant either linear or quadratic trends for most of the parameters evaluated, indicating that the best responses for morphological and physiological traits were achieved from 2.5 to 4.23 t ha^?1 with ground magnesium limestone and 2.87 to 3.45 t ha^?1 with magnesium carbonate. Positive effects of increasing rates of ground magnesium limestone and magnesium carbonate were observed on nitrogen and magnesium uptake. Aluminium concentration in the third frond decreased significantly with increasing ground magnesium limestone rate. A significant reduction of manganese uptake was also observed with increasing rates of both ameliorants. The clonal oil palm progeny exhibited a better performance on un-amended treatment. This may be explained by the significant higher root growth of this progeny. Soil acidity alleviation improved the oil palm seedling growth. These results are important for the oil palm industry and could be applied in the nursery stage as well as extended to the immature stage.     

四种土壤调理剂对镉、铅的吸附效果研究

采用等温吸附试验研究了主要原料为麦饭石(M)、蒙脱石(T)、牡蛎壳(O)和硅钙矿(S)4种土壤调理剂对溶液中镉和铅的吸附效果。结果表明,4种土壤调理剂对镉和铅的吸附均可用Langmuir方程进行描述;相比而言,4种土壤调理剂对镉吸附量的大小顺序为O调理剂>S调理剂>M调理剂>T调理剂,对铅吸附量的大小顺序为M调理剂>S调理剂>O调理剂>T调理剂;随溶液pH值的增大各调理剂的吸附量逐渐减小,尤其当Cd溶液pH值>8,Pb溶液pH值>6,各调理剂的吸附量迅速降低。     

外源硅酸钙对棕壤基础呼吸和碳酸钙含量的影响

采用室内模拟培养的方法,研究了添加硅酸钙对棕壤基础呼吸和碳酸钙含量的影响,为土壤固碳的技术选择提供理论依据。试验设硅酸钙添加量0%、1%、2%、4%和6%5个处理。结果表明,外源硅酸钙在培养前期显著抑制土壤呼吸,其抑制程度随着硅酸钙添加量的增加而增加,平均抑制率为5%(1%处理)～12%(6%处理);整个培养期间,添加硅酸钙处理的土壤碳酸钙含量较对照显著增加,且随着添加量的增加,土壤碳酸钙含量的平均增幅从83%(1%处理)上升到398%(6%处理);土壤呼吸强度和碳酸钙含量之间符合y=Ae-Bx的指数相关关系。上述结果表明,施用硅酸钙通过促进次生碳酸盐的形成从而缓解土壤CO2释放,起到固碳减排的作用。     

牛粪矿物混合蚯蚓堆肥中堆制物Pb和Cd吸附性能变化

为促进畜粪和矿物资源的生态循环利用和Pb、Cd污染土壤的原位稳定化治理,以寻求具有良好重金属吸附性能的原位稳定化修复材料为目标,该研究以高钙镁系矿物和海泡石添加下牛粪矿物混合蚯蚓堆肥为研究对象,分析堆制物性状变化及其对Pb~(2+)、Cd~(2+)的吸附性能差异。结果表明,高钙镁系矿物及海泡石添加下蚯蚓均可较好生长,蚯蚓处理可使堆制物pH值、C/N比和有机质含量降低,而使其阳离子交换量和比表面积提高;高钙镁系矿物和海泡石添加则均可提高堆制物pH值、阳离子交换量和比表面积。傅里叶红外光谱分析表明,蚯蚓处理后堆制物中醇或羧酸类物质和芳香类物质增多,而脂类和多糖类物质含量减少,且高钙镁系矿物添加使堆制物含有更多的Me-O基团。X射线衍射分析表明,蚯蚓处理后堆制物中含有更多的硅酸盐和可溶性盐;高钙镁系矿物添加则增加了堆制物中的硅酸盐含量及CaO、MgO等组分,而海泡石添加使堆制物中增加了硅酸盐含量及MgO等组分。吸附试验表明,蚯蚓处理后堆制物对Pb~(2+)、Cd~(2+)具有更大吸附量和吸持能力,且以牛粪和高钙镁系矿物混合蚯蚓堆肥中的堆制物对Pb~(2+)和Cd~(2+)吸附效果最好,其吸附率分别为77.8%、59.7%。因此,利用牛粪和高钙镁系矿物混合蚯蚓堆肥生产具有良好Pb~(2+)、Cd~(2+)吸附性能的堆制物具有一定可行性。     

不同盐分土壤环境下绿肥腐解及养分释放动态研究

通过尼龙网袋埋田法研究了绿肥苕子、黑麦草在不同盐分滨海盐渍土壤中的腐解及养分释放规律。结果表明,不同盐分地块黑麦草干物质残留率、总有机碳含量和C/N总体高于苕子。苕子氮、钾在最初15天内快速释放,不同盐分地块的残留率分别为20.4%～34.0%和13.2%～18.1%,黑麦草钾在前45天释放了近90%,氮、磷释放持续整个腐解过程。低盐分地块绿肥钠的最终残留率为5.2%～7.6%,高盐分地块为36.2%～49.2%。不同盐分地块绿肥镁、钙、锌残留率以黑麦草高于苕子。铜的释放主要集中于前45天,之后趋于停滞。镁、铁、锰分别在腐解45～60天或45～75天出现养分富集现象。整体来看,禾本科绿肥干物质及养分残留率均高于豆科绿肥,高盐分明显阻滞了绿肥氮、钙、镁、铁、锰、铜和锌养分的释放。     

Effects of Hardwood Biochar on Soil Acidity,Nutrient Dynamics,and Sweet Corn Productivity

ABSTRACT

Interest is rising in amending agricultural soils with carbon-rich materials such as charcoal to improve soil fertility. The objectives of this field study were to evaluate sugar maple hardwood charcoal (biochar) as a soil amendment. The design of the experiment was split-plot with five replications, repeated over two growing seasons with sweet corn (Zea mays L.) production. Main plots were allocated to five application amounts of biochar including 0%, 2%, 4%, 6%, and 8% by weight (0, 40, 80, 120, and 160 Mg ha^?1, respectively). Sub-plots consisted of applications of 0 or 56 kg nitrogen ha^?1 as calcium ammonium nitrate. Soil pH increased from pH 5.8 to 6.7 with biochar additions. The percent base saturation was increased due to the retention of calcium, magnesium, and potassium. Soil phosphate availability increased. Sweet corn yield in the biochar-amended plots was depressed except with the 2% application. The result of the study revealed that no more than 2% application of sugar maple hardwood biochar should be applied for sweet corn growth.     

Liming effects of beef cattle feedlot manure or compost

Abstract

Soil pH can be increased by manure or compost application because feed rations usually contain calcium carbonate. This study was conducted from 1992 to 1996 to evaluate effects of phosphorus (P) and nitrogen (N)‐based manure and compost application management strategies on soil pH level. Composted and uncomposted beef cattle (Bos taunts) feedlot manure was applied to supply N or P needs of corn (Zea mays L.) for either a one‐ or two‐year period. Phosphorus‐based manure or compost treatments also received additional fertilizer N (ammonium nitrate) to provide for a total of 151‐kg available N ha^‐1 yr^‐1. Fertilized and unfertilized checks also were included. Manure and composted manure contained about 9 g CaCO₃kg^‐1 resulting in application rates of up to 1730 kg CaCO₃ ha^‐1 in 4 years. The surface soil (0–150 mm) pH was significantly decreased with ammonium nitrate application compared to soil in the unfertilized check or to soil receiving manure or compost. Soil pH was significantly increased with the N‐based management strategy compared with the soil original level. In contrast, 4 yr of P‐based manure and compost application strategy maintained soil pH at the original level. Nitrogen‐based applications resulted in higher soil pH than P‐based. Beef cattle feedlot manure and compost can be good sources of CaCO₃ for soils requiring lime addition.     

Testing a mechanistic model. IV. Describing the effects of pH on zinc retention by soils

Samples of two soils were incubated at 60°C for 24 h with several levels of either calcium carbonate or hydrochloric acid. Zinc retention was then measured on subsamples of the treated soil over 24 h at 25°C. The results were compared with published experiments (Bar-Yosef, 1979; Harter, 1983) in which zinc retention was also measured over a range of concentrations and pH values, but using different experimental conditions. Zinc retention increased as pH increased. In all cases, this effect could be described by assuming that the ZnOH⁺ ion was retained and the effect of pH was due to the increased proportion of this ion in solution. Over most of the pH range it was not necessary to assume any contribution from a decrease in the electrostatic potential of the reacting surfaces with increasing pH. This contrasts with the effects of pH on phosphate and fluoride retention and suggests that the materials that react with zinc differ from those that react with anions. The shape of plots of zinc retention against ZnOH⁺ concentration was reproduced using a model in which it was assumed that there was a range of values of electrostatic potential. A similar model had previously been used for anions. Zinc would tend to react with the most negative end of this range and phosphate with the least negative end. This further suggests that zinc and anions may react with different materials.     

Reaction Times of Twenty Limestones

Abstract

Particle size and calcium carbonate equivalent characterize agricultural limestone. When agricultural limestone is used for horticultural container substrates, variations in pH among batches of substrate produced with the same limestone rate, as well as pH drift from initial pH, occur. Horticultural endeavors require more detailed characterization of limestone neutralization capacity than is provided for agricultural limestones. Reactivity of twenty limestones encompassing a broad range of calcium and magnesium carbonate were compared. Limestones were wet‐sieved into three particle‐diameter fractions and reacted with ammonium chloride in the presence of steam. Fine particles reacted faster than coarse; however, there was a point beyond which degree of fineness of calcitic limestone no longer affected reactivity. Dolomitic limestones were slower reacting than calcitic. Reactivity within particle fractions of dolomitic and coarse calcitic limestones varied significantly. These results indicate that particle diameter and calcium carbonate equivalent are not the only factors influencing limestone neutralization capacity.     

Spatial distribution of exchangeable bases in chernozem of Kamennaya Steppe

The high degree of base saturation and high cation exchange capacity with an appreciable dominance of calcium are related to the high carbonate content in parent rocks, high content of humus in chernozems, and abundant fine material in their profiles. These are characteristic features of prevalent soils in the Kamennaya Steppe. Almost all soils of monitoring and experimental plots have an appreciable spatial variation in exchangeable bases. The obtained data indicate that the content of adsorbed calcium in the exchangeable complex of the soil decreases with increasing shares of adsorbed magnesium and partially sodium.     

ACCUMULATION OF SILICON IN CYNODON DACTYLON X C. TRANSVAALENSIS AND POA TRIVIALIS USED AS AN OVERSEED GRASS

Calcium silicate has been used to supply silicon (Si) as a plant nutrient for enhancing crop production and the suppression of turf diseases. Research was initiated to determine the effect of calcium silicate on silicon uptake, turf quality, and its residual activity in providing plant available Si in two turfgrass systems. During 2005 and 2006, calcium silicate (CaSi, 12% Si) was applied as a topdressing at eight rates ranging from 0 to 342 kg m^?2 to a ‘Tifdwarf’ (Cynodon dactylon × C. transvaalensis Burtt Davy) green in the spring and to the same plots overseeded with ‘Wintergreen’ rough bluegrass (Poa trivialis L.) in the fall. At initiation of the study, dolomitic limestone and magnesium sulfate (MgSO₄) was applied to equilibrate calcium across all treatments based on the highest rate of CaSi. Every 28 days, treatments were rated for turf quality and then harvested to determine Si accumulation. One month after applying CaSi in 2005, Si concentration in the leaf tissue of Tifdwarf had increased linearly with increasing rates. This response continued through the months of May, June, July, August, and October with a 9%, 21%, 40%, 22% and 21% increase in Si concentration in the leaf tissue between the control and the 342 kg m^?2 rate, respectively. Although the rate response remained, there was an overall drop in average percent Si accumulation in leaf tissue across the treatments beginning three months after the first application. Similar responses were noted with the overseeded rough bluegrass with a 46%, 85%, 69%, 111% and 58% increase in Si concentration in the leaf tissue between the control and the 342 kg m^?2 rate, respectively. In contrast to the bermudagrass, over the five month period following application, the residual activity of Si in rough bluegrass remained high, suggesting that rough bluegrass might be a better Si accumulator in comparison to Tifdwarf bermudagrass. The second run of the experiment (2006–2007) and the residual trial had the same response with Si concentration in the leaf tissue increasing as the amount of CaSi applied increased. Although turfgrass quality was not well correlated to CaSi rate for Tifdwarf bermudagrass, there was an increase in quality ratings for rough bluegrass from December 2005 to April 2006.     

Barley yield and weed development as affected by crop sequence and tillage systems in a semi‐arid environment

Abstract

In order to monitor barley and weed development on a loamy sand soil subjected to different agronomic practices, field experiments were conducted for three growing seasons (1992–95) in a semi‐arid agrosystem in central Spain. For eight years, independent plots were managed with three crop sequences: barley (Hordeum vulgare L.)?vetch (Vicia sativa L.); barley? sunflower (Helianthus annuus L.); and a barley monoculture. In all cases, two tillage systems were implemented: no‐tillage and conventional tillage. In the years with standard rainfall (400 mm) an improvement in growth‐related cultivation variables and yield components of barley were observed in plots under barley?vetch rotation and/or conventional tillage. In drier conditions (<350 mm) the growth rate, crop yield and yield components of barley tended to improve under the no‐tillage system. Barley?vetch rotation and/or conventional tillage increased nitrate‐nitrogen (NO₃‐N) content in barley plants. Similar results were found for the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). In addition, the plots under crop rotation showed a weed biomass with a high concentration of N, K, and Ca in comparison with plots under monoculture. The lack of spring herbicide treatment in the no‐tillage plots led to a 3‐fold increase in weed density compared with the plots under conventional tillage.     

SPECIFIC ADSORPTION OF SILICATE AND PHOSPHATE BY SOILS

The adsorption of silicate and phosphate from pure and mixed solutions by four soils known to fix phosphate strongly has been measured. The adsorption at constant pH for each acid from its pure solution follows the Langmuir isotherm. The maximum adsorption of silicate by three of the soils from the pure solution occurs at pH 9.2, and the maximum adsorption curve for phosphate by two of the soils from its pure solution has a break in its slope at pH 6.4 and 11.6. These pHs are all just below the pK values for the dissociation of hydrogen ions from the undissociated silicic acid or the acid phosphate anions. The presence of silicate in a mixed solution, which is sufficiently concentrated in both silicate and phosphate to give maximum adsorption of either if in pure solution, does not affect the amount of phosphate adsorbed until the pH is over 6.5–7.0. At this pH the maximum adsorption curve for silicate crosses that for phosphate. The presence of phosphate in the mixed solution always depresses the adsorption of silicate. The maximum amount of silicate-plus-phosphate adsorbed from this mixed solution is either a little less than or equal to the amount of silicate adsorbed from the pure silicate solution if the pH is above 7. When silicate displaces phosphate, or phosphate displaces silicate, more moles of the displacing acid are adsorbed than moles of the displaced acid released. These results for soils are similar to those of Hingston et al. for the adsorption of silicate and phosphate by goethite.     

Diagnostic Leaf Nutrient Norms and Identification of Yield-Limiting Nutrients of Mango in Eastern Plateau and Hill Region of India

The leaf nutritional status of mango orchards was assessed using diagnosis and recommendation integrated system (DRIS). The DRIS norms, which showed higher variance and lower coefficients of variation, are found to have greater diagnostic precision. As per DRIS indices, a relative deficiency for magnesium, zinc, and boron corresponding to relative sufficiency for calcium, nitrogen, phosphorus, sulfur, and potassium was detected in 9-year-old mango orchards. For the younger orchards (6–7 year old), the order of requirement of nutrients was found to be calcium > sulfur > potassium > boron > nitrogen > phosphorus > magnesium > zinc. Boron was found as the most yield-limiting elements in all age group of plants. When the DRIS indices were compared on the basis of soil pH, calcium and magnesium were most yield-limiting nutrients below pH 5.5, while nitrogen, zinc, and boron were found to be most limiting above pH 5.5.     

Loss of nitrogen from ammoniacal fertilizers incubated under different soil and temperature conditions

Abstract

Ammonium sulfate and urea were added to three soils of widely different composition. After incubation for 28 days at 20°C, from 13 to 89% of the N from ammonium sulfate, and 8 to 71% of the N as urea were not recovered, and at 40°C, 44 to 95% of the N as ammonium sulfate, and 33 to 81% of the N as urea was not recovered as either ammonium‐N or nitrate‐N. Significantly more N was lost from a soil containing 3% calcium carbonate at pH 8.4 as compared to the two other soils containing 25 and 35% calcium carbonate, which have pH's of 7.7 and 7.5, respectively. An incubation temperature of 40°C appeared quite unfavourable for nitrification.     

铜仁市植烟土壤交换性钙镁空间分布特征及其影响因素分析

为明确贵州省铜仁市植烟土壤中交换性钙和镁的状况,以铜仁2019年植烟耕层土壤交换性钙镁为研究对象,利用多元统计学和地统计学方法分析了土壤交换性钙镁空间变异特征及其影响因素。结果表明,铜仁植烟土壤交换性钙、镁含量整体丰富,平均值分别为1.72、0.27 g·kg^-1,但仍有19.31%的交换性钙和27.59%地区的交换性镁含量处于低与极低水平。植烟土壤中钙镁比处于适宜范围的比例仅占29.70%,说明钙镁比失调较严重。土壤交换性镁含量总体呈现由西北向东南逐渐增加的趋势,土壤钙镁比总体呈现由中部向东南和西北逐渐减小的趋势,思南中部钙镁比处于最高值,江口南部与松桃南部钙镁比处于最低值。植烟土壤交换性钙、镁含量及其比值的空间变异是由结构性因素和随机性因素共同作用的结果。pH对交换性钙、镁空间变异的影响最大,分别能够独立解释其变量的41.6%、55.7%,且与交换性钙、镁分别呈现幂函数和三次函数关系,随着pH值升高,土壤中交换性钙和镁含量升高。综上,贵州铜仁植烟土壤空间分布不均匀、差异性较大,钙镁比失调比较严重,pH值对交换性钙、镁空间变异的影响最大,并与其呈极显著正相关。因此,铜仁烟区在指导钙镁施肥时要注意其空间差异性、做到分类指导,可以通过调控钙镁肥料施用量或含钙镁的改良剂调节土壤pH值来达到平衡土壤养分的目的。本研究可为铜仁市烟田钙镁养分管理提供科学依据。     

EXTRACTORS FOR ESTIMATING PLANT AVAILABLE SILICON FROM POTENTIAL SILICON FERTILIZER SOURCES

Methods to quantify plant available silicon (Si) from Si-based slags for use as fertilizers are not well defined. Although it is possible to estimate total Si from a potential Si fertilizer source; this approach does not represent how much Si is available for uptake by the plant. In this study, Si was extracted from ten sources [Wollastonite W10; calcium silicate slag from the US; calcium silicate from Canada; magnesium silicate; Excellerator; silican gel; 00-00-12 + Si (liquid source) and three types of potassium silicate with different concentrations in the liquid form, K53; K120 and AgSil^TM25] using each of the following seven methods: hydrochloric acid (HCl) plus hydrofluoric acid (HF) extraction, leaching column; sodium carbonate (Na₂CO₃–10 g L^?1) + ammonium nitrate (NH₄NO₃–16 g L^?1); citric acid (50 g dm^?3 or 5%); hydrochloric acid (0.5 N); neutral ammonium citrate (NAC); and resin (Amberlite IRC-50, pK 6.1). All the Si-containing products were added to pots at rates equal to 600 kg ha^?1 of Si based on the total Si extracted. Poa trivialis cv. ‘Darkhorse’ was grown for 24 days with these sources to determine Si plant uptake. Based on the correlation coefficients, the best extractor for available Si in solid fertilizer was determined to be Na₂CO₃ + NH₄NO₃, while for liquid fertilizers, the total Si (HCl + HF) was found to be the best. Consequently, regulatory agencies now have two extractors for estimating the plant available Si from fertilizers depending on the physical property of the material (solid or liquid).